Exterior extension for a truck cab



FIG. 1 is a perspective view of an exterior extension for truck cabs showing my new design it being understood that the broken lines are for illustrative purposes only and form no part of the claimed design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a side elevation view thereof. 

The ornamental design for an exterior extension for a truck cab, as shown and described. 